| Message ID | 20180828135324.21976-9-patrick.bellasi@arm.com (mailing list archive) |
|---|---|
| State | Changes Requested, archived |
| Headers | show |
| Series | Add utilization clamping support | expand |
On Tue, Aug 28, 2018 at 6:53 AM, Patrick Bellasi <patrick.bellasi@arm.com> wrote: > In order to properly support hierarchical resources control, the cgroup > delegation model requires that attribute writes from a child group never > fail but still are (potentially) constrained based on parent's assigned > resources. This requires to properly propagate and aggregate parent > attributes down to its descendants. > > Let's implement this mechanism by adding a new "effective" clamp value > for each task group. The effective clamp value is defined as the smaller > value between the clamp value of a group and the effective clamp value > of its parent. This represent also the clamp value which is actually > used to clamp tasks in each task group. > > Since it can be interesting for tasks in a cgroup to know exactly what > is the currently propagated/enforced configuration, the effective clamp > values are exposed to user-space by means of a new pair of read-only > attributes: cpu.util.{min,max}.effective. > > Signed-off-by: Patrick Bellasi <patrick.bellasi@arm.com> > Cc: Ingo Molnar <mingo@redhat.com> > Cc: Peter Zijlstra <peterz@infradead.org> > Cc: Tejun Heo <tj@kernel.org> > Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com> > Cc: Viresh Kumar <viresh.kumar@linaro.org> > Cc: Suren Baghdasaryan <surenb@google.com> > Cc: Todd Kjos <tkjos@google.com> > Cc: Joel Fernandes <joelaf@google.com> > Cc: Juri Lelli <juri.lelli@redhat.com> > Cc: Quentin Perret <quentin.perret@arm.com> > Cc: Dietmar Eggemann <dietmar.eggemann@arm.com> > Cc: Morten Rasmussen <morten.rasmussen@arm.com> > Cc: linux-kernel@vger.kernel.org > Cc: linux-pm@vger.kernel.org > > --- > Changes in v4: > Message-ID: <20180816140731.GD2960@e110439-lin> > - add ".effective" attributes to the default hierarchy > Others: > - small documentation fixes > - rebased on v4.19-rc1 > > Changes in v3: > Message-ID: <20180409222417.GK3126663@devbig577.frc2.facebook.com> > - new patch in v3, to implement a suggestion from v1 review > --- > Documentation/admin-guide/cgroup-v2.rst | 25 +++++- > include/linux/sched.h | 8 ++ > kernel/sched/core.c | 112 +++++++++++++++++++++++- > 3 files changed, 139 insertions(+), 6 deletions(-) > > diff --git a/Documentation/admin-guide/cgroup-v2.rst b/Documentation/admin-guide/cgroup-v2.rst > index 80ef7bdc517b..72272f58d304 100644 > --- a/Documentation/admin-guide/cgroup-v2.rst > +++ b/Documentation/admin-guide/cgroup-v2.rst > @@ -976,22 +976,43 @@ All time durations are in microseconds. > A read-write single value file which exists on non-root cgroups. > The default is "0", i.e. no bandwidth boosting. > > - The minimum utilization in the range [0, 1023]. > + The requested minimum utilization in the range [0, 1023]. > > This interface allows reading and setting minimum utilization clamp > values similar to the sched_setattr(2). This minimum utilization > value is used to clamp the task specific minimum utilization clamp. > > + cpu.util.min.effective > + A read-only single value file which exists on non-root cgroups and > + reports minimum utilization clamp value currently enforced on a task > + group. > + > + The actual minimum utilization in the range [0, 1023]. > + > + This value can be lower then cpu.util.min in case a parent cgroup > + is enforcing a more restrictive clamping on minimum utilization. IMHO if cpu.util.min=0 means "no restrictions" on UCLAMP_MIN then calling parent's lower cpu.util.min value "more restrictive clamping" is confusing. I would suggest to rephrase this to smth like "...in case a parent cgroup requires lower cpu.util.min clamping." > + > cpu.util.max > A read-write single value file which exists on non-root cgroups. > The default is "1023". i.e. no bandwidth clamping > > - The maximum utilization in the range [0, 1023]. > + The requested maximum utilization in the range [0, 1023]. > > This interface allows reading and setting maximum utilization clamp > values similar to the sched_setattr(2). This maximum utilization > value is used to clamp the task specific maximum utilization clamp. > > + cpu.util.max.effective > + A read-only single value file which exists on non-root cgroups and > + reports maximum utilization clamp value currently enforced on a task > + group. > + > + The actual maximum utilization in the range [0, 1023]. > + > + This value can be lower then cpu.util.max in case a parent cgroup > + is enforcing a more restrictive clamping on max utilization. > + > + > Memory > ------ > > diff --git a/include/linux/sched.h b/include/linux/sched.h > index dc39b67a366a..2da130d17e70 100644 > --- a/include/linux/sched.h > +++ b/include/linux/sched.h > @@ -591,6 +591,14 @@ struct sched_dl_entity { > struct uclamp_se { > unsigned int value; > unsigned int group_id; > + /* > + * Effective task (group) clamp value. > + * For task groups is the value (eventually) enforced by a parent task > + * group. > + */ > + struct { > + unsigned int value; > + } effective; > }; > > union rcu_special { > diff --git a/kernel/sched/core.c b/kernel/sched/core.c > index dcbf22abd0bf..b2d438b6484b 100644 > --- a/kernel/sched/core.c > +++ b/kernel/sched/core.c > @@ -1254,6 +1254,8 @@ static inline int alloc_uclamp_sched_group(struct task_group *tg, > > for (clamp_id = 0; clamp_id < UCLAMP_CNT; ++clamp_id) { > uc_se = &tg->uclamp[clamp_id]; > + uc_se->effective.value = > + parent->uclamp[clamp_id].effective.value; > uc_se->value = parent->uclamp[clamp_id].value; > uc_se->group_id = parent->uclamp[clamp_id].group_id; > } > @@ -1415,6 +1417,7 @@ static void __init init_uclamp(void) > #ifdef CONFIG_UCLAMP_TASK_GROUP > /* Init root TG's clamp group */ > uc_se = &root_task_group.uclamp[clamp_id]; > + uc_se->effective.value = uclamp_none(clamp_id); > uc_se->value = uclamp_none(clamp_id); > uc_se->group_id = 0; > #endif > @@ -7226,6 +7229,68 @@ static void cpu_cgroup_attach(struct cgroup_taskset *tset) > } > > #ifdef CONFIG_UCLAMP_TASK_GROUP > +/** > + * cpu_util_update_hier: propagete effective clamp down the hierarchy typo: propagate > + * @css: the task group to update > + * @clamp_id: the clamp index to update > + * @value: the new task group clamp value > + * > + * The effective clamp for a TG is expected to track the most restrictive > + * value between the TG's clamp value and it's parent effective clamp value. > + * This method achieve that: > + * 1. updating the current TG effective value > + * 2. walking all the descendant task group that needs an update > + * > + * A TG's effective clamp needs to be updated when its current value is not > + * matching the TG's clamp value. In this case indeed either: > + * a) the parent has got a more relaxed clamp value > + * thus potentially we can relax the effective value for this group > + * b) the parent has got a more strict clamp value > + * thus potentially we have to restrict the effective value of this group > + * > + * Restriction and relaxation of current TG's effective clamp values needs to > + * be propagated down to all the descendants. When a subgroup is found which > + * has already its effective clamp value matching its clamp value, then we can > + * safely skip all its descendants which are granted to be already in sync. > + */ > +static void cpu_util_update_hier(struct cgroup_subsys_state *css, > + int clamp_id, int value) > +{ > + struct cgroup_subsys_state *top_css = css; > + struct uclamp_se *uc_se, *uc_parent; > + > + css_for_each_descendant_pre(css, top_css) { > + /* > + * The first visited task group is top_css, which clamp value > + * is the one passed as parameter. For descendent task > + * groups we consider their current value. > + */ > + uc_se = &css_tg(css)->uclamp[clamp_id]; > + if (css != top_css) > + value = uc_se->value; > + /* > + * Skip the whole subtrees if the current effective clamp is > + * alredy matching the TG's clamp value. typo: already > + * In this case, all the subtrees already have top_value, or a > + * more restrictive, as effective clamp. > + */ > + uc_parent = &css_tg(css)->parent->uclamp[clamp_id]; > + if (uc_se->effective.value == value && > + uc_parent->effective.value >= value) { > + css = css_rightmost_descendant(css); > + continue; > + } > + > + /* Propagate the most restrictive effective value */ > + if (uc_parent->effective.value < value) > + value = uc_parent->effective.value; > + if (uc_se->effective.value == value) > + continue; > + > + uc_se->effective.value = value; > + } > +} > + > static int cpu_util_min_write_u64(struct cgroup_subsys_state *css, > struct cftype *cftype, u64 min_value) > { > @@ -7245,6 +7310,9 @@ static int cpu_util_min_write_u64(struct cgroup_subsys_state *css, > if (tg->uclamp[UCLAMP_MAX].value < min_value) > goto out; > > + /* Update effective clamps to track the most restrictive value */ > + cpu_util_update_hier(css, UCLAMP_MIN, min_value); > + > out: > rcu_read_unlock(); > > @@ -7270,6 +7338,9 @@ static int cpu_util_max_write_u64(struct cgroup_subsys_state *css, > if (tg->uclamp[UCLAMP_MIN].value > max_value) > goto out; > > + /* Update effective clamps to track the most restrictive value */ > + cpu_util_update_hier(css, UCLAMP_MAX, max_value); > + > out: > rcu_read_unlock(); > > @@ -7277,14 +7348,17 @@ static int cpu_util_max_write_u64(struct cgroup_subsys_state *css, > } > > static inline u64 cpu_uclamp_read(struct cgroup_subsys_state *css, > - enum uclamp_id clamp_id) > + enum uclamp_id clamp_id, > + bool effective) > { > struct task_group *tg; > u64 util_clamp; > > rcu_read_lock(); > tg = css_tg(css); > - util_clamp = tg->uclamp[clamp_id].value; > + util_clamp = effective > + ? tg->uclamp[clamp_id].effective.value > + : tg->uclamp[clamp_id].value; > rcu_read_unlock(); > > return util_clamp; > @@ -7293,13 +7367,25 @@ static inline u64 cpu_uclamp_read(struct cgroup_subsys_state *css, > static u64 cpu_util_min_read_u64(struct cgroup_subsys_state *css, > struct cftype *cft) > { > - return cpu_uclamp_read(css, UCLAMP_MIN); > + return cpu_uclamp_read(css, UCLAMP_MIN, false); > } > > static u64 cpu_util_max_read_u64(struct cgroup_subsys_state *css, > struct cftype *cft) > { > - return cpu_uclamp_read(css, UCLAMP_MAX); > + return cpu_uclamp_read(css, UCLAMP_MAX, false); > +} > + > +static u64 cpu_util_min_effective_read_u64(struct cgroup_subsys_state *css, > + struct cftype *cft) > +{ > + return cpu_uclamp_read(css, UCLAMP_MIN, true); > +} > + > +static u64 cpu_util_max_effective_read_u64(struct cgroup_subsys_state *css, > + struct cftype *cft) > +{ > + return cpu_uclamp_read(css, UCLAMP_MAX, true); > } > #endif /* CONFIG_UCLAMP_TASK_GROUP */ > > @@ -7647,11 +7733,19 @@ static struct cftype cpu_legacy_files[] = { > .read_u64 = cpu_util_min_read_u64, > .write_u64 = cpu_util_min_write_u64, > }, > + { > + .name = "util.min.effective", > + .read_u64 = cpu_util_min_effective_read_u64, > + }, > { > .name = "util.max", > .read_u64 = cpu_util_max_read_u64, > .write_u64 = cpu_util_max_write_u64, > }, > + { > + .name = "util.max.effective", > + .read_u64 = cpu_util_max_effective_read_u64, > + }, > #endif > { } /* Terminate */ > }; > @@ -7827,12 +7921,22 @@ static struct cftype cpu_files[] = { > .read_u64 = cpu_util_min_read_u64, > .write_u64 = cpu_util_min_write_u64, > }, > + { > + .name = "util.min.effective", > + .flags = CFTYPE_NOT_ON_ROOT, > + .read_u64 = cpu_util_min_effective_read_u64, > + }, > { > .name = "util_max", > .flags = CFTYPE_NOT_ON_ROOT, > .read_u64 = cpu_util_max_read_u64, > .write_u64 = cpu_util_max_write_u64, > }, > + { > + .name = "util.max.effective", > + .flags = CFTYPE_NOT_ON_ROOT, > + .read_u64 = cpu_util_max_effective_read_u64, > + }, > #endif > { } /* terminate */ > }; > -- > 2.18.0 >
Hello, Patrick. Can we first concentrate on getting in the non-cgroup part first? The feature has to make sense without cgroup too and I think it'd be a lot easier to discuss cgroup details once the scheduler core side is settled. Thanks.
On 11-Sep 08:18, Tejun Heo wrote: > Hello, Patrick. Hi Tejun, > Can we first concentrate on getting in the non-cgroup part first? That's the reason why I've reordered (as per your request) the series to have all the core and non-cgroup related bits at the beginning. There are a couple of patches at the end of this series which can be anticipated but, apart from those, the cgroup code is very well self-contained within patches 7-12. > The feature has to make sense without cgroup too Indeed, this is what I worked on since you pointed out in v1 that there must be a meaningful non-cgroup API and that's what we have since v2. > and I think it'd be a lot easier to discuss cgroup details once the > scheduler core side is settled. IMHO, developing the cgroup interface on top of the core bits is quite important to ensure that we have effective data structures and implementation which can satisfy both worlds. My question is: IF the scheduler maintainers are going to be happy with the overall design for the core bits, are you happy to start the review of the cgroups bits before the core ones are (eventually) merged? Cheers, Patrick
Hello, Patrick. On Tue, Sep 11, 2018 at 05:26:24PM +0100, Patrick Bellasi wrote: > My question is: IF the scheduler maintainers are going to be happy > with the overall design for the core bits, are you happy to start the > review of the cgroups bits before the core ones are (eventually) merged? Yeah, sure, once the feature is more or less agreed on the scheduler core side, we can delve into how it should be represented in cgroup. Thanks.
On 08-Sep 20:02, Suren Baghdasaryan wrote: > On Tue, Aug 28, 2018 at 6:53 AM, Patrick Bellasi > <patrick.bellasi@arm.com> wrote: [...] > > + cpu.util.min.effective > > + A read-only single value file which exists on non-root cgroups and > > + reports minimum utilization clamp value currently enforced on a task > > + group. > > + > > + The actual minimum utilization in the range [0, 1023]. > > + > > + This value can be lower then cpu.util.min in case a parent cgroup > > + is enforcing a more restrictive clamping on minimum utilization. > > IMHO if cpu.util.min=0 means "no restrictions" on UCLAMP_MIN then > calling parent's lower cpu.util.min value "more restrictive clamping" > is confusing. I would suggest to rephrase this to smth like "...in > case a parent cgroup requires lower cpu.util.min clamping." Right, it's slightly confusing... still I would like to call out that a parent group can enforce something on its children. What about: "... a parent cgroup allows only smaller minimum utilization values." Is that less confusing ? Otherwise I think your proposal could work too. [...] > > #ifdef CONFIG_UCLAMP_TASK_GROUP > > +/** > > + * cpu_util_update_hier: propagete effective clamp down the hierarchy > > typo: propagate +1 [...] > > + * Skip the whole subtrees if the current effective clamp is > > + * alredy matching the TG's clamp value. > > typo: already +1 Cheers, Patrick
On Wed, Sep 12, 2018 at 5:51 AM, Patrick Bellasi <patrick.bellasi@arm.com> wrote: > On 08-Sep 20:02, Suren Baghdasaryan wrote: >> On Tue, Aug 28, 2018 at 6:53 AM, Patrick Bellasi >> <patrick.bellasi@arm.com> wrote: > > [...] > >> > + cpu.util.min.effective >> > + A read-only single value file which exists on non-root cgroups and >> > + reports minimum utilization clamp value currently enforced on a task >> > + group. >> > + >> > + The actual minimum utilization in the range [0, 1023]. >> > + >> > + This value can be lower then cpu.util.min in case a parent cgroup >> > + is enforcing a more restrictive clamping on minimum utilization. >> >> IMHO if cpu.util.min=0 means "no restrictions" on UCLAMP_MIN then >> calling parent's lower cpu.util.min value "more restrictive clamping" >> is confusing. I would suggest to rephrase this to smth like "...in >> case a parent cgroup requires lower cpu.util.min clamping." > > Right, it's slightly confusing... still I would like to call out that > a parent group can enforce something on its children. What about: > > "... a parent cgroup allows only smaller minimum utilization values." > > Is that less confusing ? SGTM. > > Otherwise I think your proposal could work too. > > [...] > >> > #ifdef CONFIG_UCLAMP_TASK_GROUP >> > +/** >> > + * cpu_util_update_hier: propagete effective clamp down the hierarchy >> >> typo: propagate > > +1 > > [...] > >> > + * Skip the whole subtrees if the current effective clamp is >> > + * alredy matching the TG's clamp value. >> >> typo: already > > +1 > > > Cheers, > Patrick > > -- > #include <best/regards.h> > > Patrick Bellasi
diff --git a/Documentation/admin-guide/cgroup-v2.rst b/Documentation/admin-guide/cgroup-v2.rst index 80ef7bdc517b..72272f58d304 100644 --- a/Documentation/admin-guide/cgroup-v2.rst +++ b/Documentation/admin-guide/cgroup-v2.rst @@ -976,22 +976,43 @@ All time durations are in microseconds. A read-write single value file which exists on non-root cgroups. The default is "0", i.e. no bandwidth boosting. - The minimum utilization in the range [0, 1023]. + The requested minimum utilization in the range [0, 1023]. This interface allows reading and setting minimum utilization clamp values similar to the sched_setattr(2). This minimum utilization value is used to clamp the task specific minimum utilization clamp. + cpu.util.min.effective + A read-only single value file which exists on non-root cgroups and + reports minimum utilization clamp value currently enforced on a task + group. + + The actual minimum utilization in the range [0, 1023]. + + This value can be lower then cpu.util.min in case a parent cgroup + is enforcing a more restrictive clamping on minimum utilization. + cpu.util.max A read-write single value file which exists on non-root cgroups. The default is "1023". i.e. no bandwidth clamping - The maximum utilization in the range [0, 1023]. + The requested maximum utilization in the range [0, 1023]. This interface allows reading and setting maximum utilization clamp values similar to the sched_setattr(2). This maximum utilization value is used to clamp the task specific maximum utilization clamp. + cpu.util.max.effective + A read-only single value file which exists on non-root cgroups and + reports maximum utilization clamp value currently enforced on a task + group. + + The actual maximum utilization in the range [0, 1023]. + + This value can be lower then cpu.util.max in case a parent cgroup + is enforcing a more restrictive clamping on max utilization. + + Memory ------ diff --git a/include/linux/sched.h b/include/linux/sched.h index dc39b67a366a..2da130d17e70 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -591,6 +591,14 @@ struct sched_dl_entity { struct uclamp_se { unsigned int value; unsigned int group_id; + /* + * Effective task (group) clamp value. + * For task groups is the value (eventually) enforced by a parent task + * group. + */ + struct { + unsigned int value; + } effective; }; union rcu_special { diff --git a/kernel/sched/core.c b/kernel/sched/core.c index dcbf22abd0bf..b2d438b6484b 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -1254,6 +1254,8 @@ static inline int alloc_uclamp_sched_group(struct task_group *tg, for (clamp_id = 0; clamp_id < UCLAMP_CNT; ++clamp_id) { uc_se = &tg->uclamp[clamp_id]; + uc_se->effective.value = + parent->uclamp[clamp_id].effective.value; uc_se->value = parent->uclamp[clamp_id].value; uc_se->group_id = parent->uclamp[clamp_id].group_id; } @@ -1415,6 +1417,7 @@ static void __init init_uclamp(void) #ifdef CONFIG_UCLAMP_TASK_GROUP /* Init root TG's clamp group */ uc_se = &root_task_group.uclamp[clamp_id]; + uc_se->effective.value = uclamp_none(clamp_id); uc_se->value = uclamp_none(clamp_id); uc_se->group_id = 0; #endif @@ -7226,6 +7229,68 @@ static void cpu_cgroup_attach(struct cgroup_taskset *tset) } #ifdef CONFIG_UCLAMP_TASK_GROUP +/** + * cpu_util_update_hier: propagete effective clamp down the hierarchy + * @css: the task group to update + * @clamp_id: the clamp index to update + * @value: the new task group clamp value + * + * The effective clamp for a TG is expected to track the most restrictive + * value between the TG's clamp value and it's parent effective clamp value. + * This method achieve that: + * 1. updating the current TG effective value + * 2. walking all the descendant task group that needs an update + * + * A TG's effective clamp needs to be updated when its current value is not + * matching the TG's clamp value. In this case indeed either: + * a) the parent has got a more relaxed clamp value + * thus potentially we can relax the effective value for this group + * b) the parent has got a more strict clamp value + * thus potentially we have to restrict the effective value of this group + * + * Restriction and relaxation of current TG's effective clamp values needs to + * be propagated down to all the descendants. When a subgroup is found which + * has already its effective clamp value matching its clamp value, then we can + * safely skip all its descendants which are granted to be already in sync. + */ +static void cpu_util_update_hier(struct cgroup_subsys_state *css, + int clamp_id, int value) +{ + struct cgroup_subsys_state *top_css = css; + struct uclamp_se *uc_se, *uc_parent; + + css_for_each_descendant_pre(css, top_css) { + /* + * The first visited task group is top_css, which clamp value + * is the one passed as parameter. For descendent task + * groups we consider their current value. + */ + uc_se = &css_tg(css)->uclamp[clamp_id]; + if (css != top_css) + value = uc_se->value; + /* + * Skip the whole subtrees if the current effective clamp is + * alredy matching the TG's clamp value. + * In this case, all the subtrees already have top_value, or a + * more restrictive, as effective clamp. + */ + uc_parent = &css_tg(css)->parent->uclamp[clamp_id]; + if (uc_se->effective.value == value && + uc_parent->effective.value >= value) { + css = css_rightmost_descendant(css); + continue; + } + + /* Propagate the most restrictive effective value */ + if (uc_parent->effective.value < value) + value = uc_parent->effective.value; + if (uc_se->effective.value == value) + continue; + + uc_se->effective.value = value; + } +} + static int cpu_util_min_write_u64(struct cgroup_subsys_state *css, struct cftype *cftype, u64 min_value) { @@ -7245,6 +7310,9 @@ static int cpu_util_min_write_u64(struct cgroup_subsys_state *css, if (tg->uclamp[UCLAMP_MAX].value < min_value) goto out; + /* Update effective clamps to track the most restrictive value */ + cpu_util_update_hier(css, UCLAMP_MIN, min_value); + out: rcu_read_unlock(); @@ -7270,6 +7338,9 @@ static int cpu_util_max_write_u64(struct cgroup_subsys_state *css, if (tg->uclamp[UCLAMP_MIN].value > max_value) goto out; + /* Update effective clamps to track the most restrictive value */ + cpu_util_update_hier(css, UCLAMP_MAX, max_value); + out: rcu_read_unlock(); @@ -7277,14 +7348,17 @@ static int cpu_util_max_write_u64(struct cgroup_subsys_state *css, } static inline u64 cpu_uclamp_read(struct cgroup_subsys_state *css, - enum uclamp_id clamp_id) + enum uclamp_id clamp_id, + bool effective) { struct task_group *tg; u64 util_clamp; rcu_read_lock(); tg = css_tg(css); - util_clamp = tg->uclamp[clamp_id].value; + util_clamp = effective + ? tg->uclamp[clamp_id].effective.value + : tg->uclamp[clamp_id].value; rcu_read_unlock(); return util_clamp; @@ -7293,13 +7367,25 @@ static inline u64 cpu_uclamp_read(struct cgroup_subsys_state *css, static u64 cpu_util_min_read_u64(struct cgroup_subsys_state *css, struct cftype *cft) { - return cpu_uclamp_read(css, UCLAMP_MIN); + return cpu_uclamp_read(css, UCLAMP_MIN, false); } static u64 cpu_util_max_read_u64(struct cgroup_subsys_state *css, struct cftype *cft) { - return cpu_uclamp_read(css, UCLAMP_MAX); + return cpu_uclamp_read(css, UCLAMP_MAX, false); +} + +static u64 cpu_util_min_effective_read_u64(struct cgroup_subsys_state *css, + struct cftype *cft) +{ + return cpu_uclamp_read(css, UCLAMP_MIN, true); +} + +static u64 cpu_util_max_effective_read_u64(struct cgroup_subsys_state *css, + struct cftype *cft) +{ + return cpu_uclamp_read(css, UCLAMP_MAX, true); } #endif /* CONFIG_UCLAMP_TASK_GROUP */ @@ -7647,11 +7733,19 @@ static struct cftype cpu_legacy_files[] = { .read_u64 = cpu_util_min_read_u64, .write_u64 = cpu_util_min_write_u64, }, + { + .name = "util.min.effective", + .read_u64 = cpu_util_min_effective_read_u64, + }, { .name = "util.max", .read_u64 = cpu_util_max_read_u64, .write_u64 = cpu_util_max_write_u64, }, + { + .name = "util.max.effective", + .read_u64 = cpu_util_max_effective_read_u64, + }, #endif { } /* Terminate */ }; @@ -7827,12 +7921,22 @@ static struct cftype cpu_files[] = { .read_u64 = cpu_util_min_read_u64, .write_u64 = cpu_util_min_write_u64, }, + { + .name = "util.min.effective", + .flags = CFTYPE_NOT_ON_ROOT, + .read_u64 = cpu_util_min_effective_read_u64, + }, { .name = "util_max", .flags = CFTYPE_NOT_ON_ROOT, .read_u64 = cpu_util_max_read_u64, .write_u64 = cpu_util_max_write_u64, }, + { + .name = "util.max.effective", + .flags = CFTYPE_NOT_ON_ROOT, + .read_u64 = cpu_util_max_effective_read_u64, + }, #endif { } /* terminate */ };
In order to properly support hierarchical resources control, the cgroup delegation model requires that attribute writes from a child group never fail but still are (potentially) constrained based on parent's assigned resources. This requires to properly propagate and aggregate parent attributes down to its descendants. Let's implement this mechanism by adding a new "effective" clamp value for each task group. The effective clamp value is defined as the smaller value between the clamp value of a group and the effective clamp value of its parent. This represent also the clamp value which is actually used to clamp tasks in each task group. Since it can be interesting for tasks in a cgroup to know exactly what is the currently propagated/enforced configuration, the effective clamp values are exposed to user-space by means of a new pair of read-only attributes: cpu.util.{min,max}.effective. Signed-off-by: Patrick Bellasi <patrick.bellasi@arm.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Tejun Heo <tj@kernel.org> Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com> Cc: Viresh Kumar <viresh.kumar@linaro.org> Cc: Suren Baghdasaryan <surenb@google.com> Cc: Todd Kjos <tkjos@google.com> Cc: Joel Fernandes <joelaf@google.com> Cc: Juri Lelli <juri.lelli@redhat.com> Cc: Quentin Perret <quentin.perret@arm.com> Cc: Dietmar Eggemann <dietmar.eggemann@arm.com> Cc: Morten Rasmussen <morten.rasmussen@arm.com> Cc: linux-kernel@vger.kernel.org Cc: linux-pm@vger.kernel.org --- Changes in v4: Message-ID: <20180816140731.GD2960@e110439-lin> - add ".effective" attributes to the default hierarchy Others: - small documentation fixes - rebased on v4.19-rc1 Changes in v3: Message-ID: <20180409222417.GK3126663@devbig577.frc2.facebook.com> - new patch in v3, to implement a suggestion from v1 review --- Documentation/admin-guide/cgroup-v2.rst | 25 +++++- include/linux/sched.h | 8 ++ kernel/sched/core.c | 112 +++++++++++++++++++++++- 3 files changed, 139 insertions(+), 6 deletions(-)